Glossary

Angioplasty

The surgical repair of a blood vessel, either by inserting a balloon-tipped catheter to unblock it, or by reconstructing or replacing part of the vessel.

Antibody

A Y-shaped protein on the surface of B cells that is secreted into the blood or lymph in response to an antigenic stimulus, such as a bacterium, virus, parasite, or transplanted organ, and that neutralizes the antigen by binding specifically to it.

Atom

Basic unit of matter that consists of a dense, central nucleus surrounded by a cloud of electrons.

Bioluminescence

Emissions of visible light such by living organisms as the firefly and various fish, fungi, and bacteria.

Biopsy

Process of removing a small amount of tissue from the body for examination under a microscope.

Calcification

A process by which non-cellular material in the body becomes hardened due to deposits of calcium and other materials.

Carcinogenic

A cancer-causing substance or agent.

Catheterization

In medicine, a catheter is a tube that can be inserted into a body cavity, duct, or vessel. The process of inserting a catheter is catheterization.

Cellular

Relating to, or consisting of cells.

Celular

Relativo ou constituído de células.

Contrast agent

A substance used to enhance the contrast of structures or fluids within the body in medical imaging.

Decay

Decay of an atomic nucleus. To undergo radioactive disintegration.

Dementia

Term for memory loss and decline in intellectual functioning that is severe enough to interfere with an individual's ability to perform routine tasks.

Density

The mass of a material divided by its volume.

Electromagnetic radiation

Form of energy exhibiting wave-like behavior as it travels through space and has both electric and magnetic field components.

Fluorescence

The emission of electromagnetic radiation, especially of visible light, stimulated in a substance by the absorption of incident radiation and persisting only as long as the stimulating radiation is continued.

Gamma rays

Gamma radiation i.e. electromagnetic radiation of very short wavelength emitted by any source, esp. the portion of the electromagnetic spectrum with a wavelength less than about 10-11 meters.

Gene

A hereditary unit consisting of a sequence of DNA that occupies a specific location on a chromosome and determines a particular characteristic in an organism. Genes undergo mutation when their DNA sequence changes.

Gene expression

Conversion of the information encoded in a gene first into messenger RNA and then to a protein.

Half-life

The time taken for half of the atoms in a radioactive material to undergo decay.

Imaging agent

A molecule that can bind both to a radiotracer and to a molecule of interest, such as cancer cells, within the body so that they may be imaged with molecular imaging technologies.

Ionization

Ionization is the process whereby an atom or molecule gains either a positive or negative charge.

Ionizing radiation

Radiation of sufficient energy to dissociate atoms or molecules into electrically charged atoms or radicals in the irradiated material.

Isotope

One of two or more atoms having the same atomic number but different mass numbers.

Ligand

An ion, a molecule, or a molecular group that binds to another chemical entity to form a larger complex.

Metabolism

Set of chemical reactions that occur in living organisms to convert fuel into energy.

Metastasis

Process by which cancer spreads from the place at which it first arose as a primary tumor to distant locations in the body.

Metastatic

Relating to metastasis.

Molecular

Relating to, or consisting of molecules.

Molecule

Smallest particle of a substance that retains the chemical and physical properties of the substance and is composed of two or more atoms or a group of similar or different atoms held together by chemical forces.

mSV

milliSievert; equivalent dose of ionizing radiation.

Natural background radiation

Is constantly present in the environment and is emitted from a variety of natural sources.

Nuclear medicine

Special area of medicine and medical imaging that uses radionuclides and relies on the process of radioactive decay in the diagnosis and treatment of disease.

Peer-reviewed

Generic term for a process of self-regulation by a profession or a process of evaluation involving qualified individuals within the relevant field. Peer review methods are employed to maintain standards, improve performance and provide credibility. The term is often used to denote prepublication reviews of academic papers.

PET

A device that produces cross-sectional x-rays of metabolic processes by means of positron emission tomography.

Polyp

Abnormal growth of tissue projecting from a mucous membrane. Polyps are commonly found in the stomach, nose, urinary bladder etc.

Proton

A positively charged particle that is a fundamental component of the nucleus of all atoms.

Radiolabel

A radioactive isotope used as a tracer (radiotracer).

Radionuclide

Nuclide that disintegrates with the emission of corpuscular or electromagnetic radiations.

Radiopharmaceutical

A drug that emits radioactivity and is also called radiotracer.

Radiotracer

A compound that includes a radioactive atom or isotope that is used as an imaging agent in a branch of molecular imaging called nuclear medicine. Radiotracers are introduced into the body where they accumulate in a target organ or attach to specific cells and are detected by a device, which creates pictures of how the agent is distributed in the body.

Sedation

Sedation is the act of calming by administration of a sedative. A sedative is a medication that commonly induces the nervous system to calm.

Sonogram

An image, as of an unborn fetus or an internal body organ, produced by ultrasonography. Also called echogram, sonograph, ultrasonogram.

SPECT

Single photon emission computed tomography (SPECT, or less commonly, SPET) is a nuclear imaging technique using gamma rays.

Transducer probe

An instrument that locates tissues or organs inside the body by using ultrasound.

Unstable

Decaying with relatively short lifetime. Used of subatomic particles.

X-ray

Relatively high-energy photons, used for their penetrating power in radiography, radiology, radiotherapy, and scientific research.

About Us

This website is an initiative of Siemens Healthineers to provide patients and healthcare professionals with information about the use of radiation in medical imaging.